Isolation And Identification Of Manganese-Resistant Strains And Mechanism Of Manganese Adaptation

Manganese is one of the essential elements of the organism,can be used as a cofactor for a variety of enzymes and essential for metabolism of lipids,proteins,and etc.,however,it can cause a range of diseases such as Parkinson's Disease,neurodegenerative diseases when the body with high manganese content.At present,the rapid development of the mining of manganese ore and Electrolytic manganese industry and Iron and Steel Smelting industry,resulted in increasing the metal content of the soil and water in the surrounding areas which caused serious environmental pollution.It has a long treatment cycle and difficult to completely remove manganese pollution by using the ways of traditional physical and chemical repair,so microbiological repair has a broad developing prospect with the advantages of no secondary pollution and low cost of low concentration metal.This study is the isolation and identification of manganese resistant bacteria and find the tolerance mechanism.The results are as follows:7 strains of bacteria were isolated from the soil of a manganese smelting area in Zhaiying town of Songtao county,Guizhou Province.Named S1?S2?S7?S15?S16?S20 and S23.These strains could survive on medium with Mn2+ concentration more than 1800 mg/L.And the resistant concentration of Mn2+ was as high as 2200 mg/L in two strains named S7 and S16.These strains were classified to be Agrobacterium tumefaciens,Bacillus safensis,Rhizobium sp.and Arthrobacter oxydans based on the morphology,biochemical characters and 16 S rDNA gene sequences similarity.Flame atomic absorption spectrophotometry was used to detect the removal rate of high resistance strain S7 and S16 with Mn content is 250 mg/L.When bacteria culture in no longer grow date,we measured the data of average manganese content remains for S7 and S16 were 44.53 and 56.83 mg/L,respectively.And the removal rate were 82% and 77%,respectively.One high tolerance of bacteria(S7)was chose for studying the adaptability ofmanganese salt.With the stress treatment of the manganese salt with concentration of 0 mg/L,250 mg/L and 500 mg/L,respectively,we measured the growth curves and electrical conductivity of strain S7.And superoxide dismutase(SOD)activity was measured by the method of xanthine oxidase and catalase(CAT)activity was determined by ammonium molybdate method.The results showed that: the growth rate of bacteria was fast without the Mn2+stress,and enter the stable period at 14 to18 hours;the growth rate of the strain was slow down under the condition of Mn2+stress;the activity of SOD and CAT in the strain was increased at 10-18 hours;while the conductivity had a little change.The transcriptome sequencing analysis was performed in the S7 under 250mg/L manganese-treated.The original data were filtration with NGSQC and we obtained the clean data.Using DEGseq to do the difference analysis of gene.We found that 1139 genes were differential expressed in two groups,191 gene expression was down-regulated and 233 genes were up-regulated among the 423 gene which RPKM were not less than 400.Go gene function enrichment analysis and KEGG pathway Biological pathway analysis were performed in the all of the differentially expressed genes.It was found that the differentially expressed genes were mainly involved in carbohydrate metabolism,lipid metabolism,translation,energy metabolism,nucleotide metabolism,Amino acid metabolism,membrane transport,signal transduction.the cotA encoding a manganese-oxidizing protein with copper oxidase was up-regulated and can oxidize the solution of Mn2+,forming precipitation.In summary,we obtained high manganese tolerance of bacteria from the manganese contaminated soil,it was expanded excellent bacteria resources for microbial repair of manganese pollution;Meanwhile,under the condition of manganese stress,the bacteria can adapt to the manganese environment by metabolism,which would provide a theoretical basis for the repair of manganese pollution by bacteria.